This invention relates in general to the construction of devices for folding strip materials, particularly for use in association with sewing machines and, in particular, to a new and useful material folding device which comprises a substantially U-shape guide which tapers from a widened entrance end to a narrowed discharge end, wherein, a material strip is insertable in the guide and held by a positioning plate as it is moved therealong to fold it into a U-shape configuration and which further includes a folding element of substantially W-shape configuration with a central folding web which engages into the guide to hold the material therein and includes leg portions which engage over the guide.